OUTLINE: DNA is examined for unstable elements (microsatellite instability and loss of heterozygosity) by analyzing at least 10 separate (CA)n-repeats localized to 5 separate chromosomes (5q, 8p, 15, 17p, and 18q). Loss of heterozygosity is analyzed for at least four chromosomal arms (5q, 8p, 17p, and 18q) and later other chromosomes (e.g., 1, 14, and 22). Immunohistochemistry is used to test for the presence or absence of the genes involved in DNA mismatch repair (hMLH1 and hMSH2).